02. Primary Diagonal

#include <iostream>
using namespace std;

#define SIZE 100

int main()
{
  int matrix[SIZE][SIZE];

  int sum_left = 0, sum_right = 0;
  int size;
  cin >> size;
  for(int i = 0; i < size ; i++)
  {
  for(int j = 0; j < size; j++)
  {
    cin >> matrix[i][j];
    if(i==j)
      sum_left += matrix[i][j];
    if((i+j) == SIZE-1)
      sum_right += matrix[i][j];
    }
  }

  cout << sum_left << endl;
  return 0;
}